Reproductive Isolation
Reproductive isolation explained in an easy to understand way:
Imagine trying to use a charging cable from an old phone with a new phone that has a completely different port type. This is similar to reproductive isolation, where two populations evolve distinct characteristics preventing them from successfully interbreeding. Just as the old and new phone ports are incompatible for charging, the evolved differences in these populations prevent them from producing fertile offspring together.
Practice Version
Reproductive Isolation: Occurs when two populations evolve to the point that they cannot interbreed to produce fertile offspring. Reproductive isolation is when different species cannot have babies together or their babies can't have babies.